KIEV, Ukraine {AP} Chernobyl was shut down forever with the flip of a switch Friday, shifting attention to needed repairs on the sarcophagus covering the nuclear plant's ruined reactor, which is leaking radiation 14 years after the world's worst nuclear accident.

The closing of Chernobyl's last working reactor was intended to prevent disasters like the one that sent a radioactive cloud across Europe, affecting millions and leaving a poisoned zone in this former Soviet republic.

President Leonid Kuchma, issuing the order to halt the reactor, alluded to the difficult work still ahead, saying: "This menacing page of the book of modern history cannot be considered closed."

At a state ceremony in Kiev, Kuchma gave the order to halt the reactor over a video linkup with the plant 84 miles away. At 1:16 p.m., Chernobyl shift chief Oleksandr Yelchishchev turned a switch, sending containment rods sliding into the core of reactor No. 3. Within seconds, a dial showed the atomic reaction in the core dropping to zero.

Kuchma asserted that energy-starved Ukraine was "forsaking a part of our national interests for the sake of global safety."

President Clinton, in a taped address released by the U.S. Embassy in Kiev, called it a "triumph for the common good."

"America is on your side. We wish you God speed," he said, adding in Ukrainian: "Slava Ukrayini (Glory to Ukraine)!"

On April 26, 1986, Chernobyl's reactor No. 4 exploded and caught fire, contaminating vast areas of Ukraine, Russia and Belarus all formerly of the Soviet Union and spewing a radioactive cloud over Europe.

The Kremlin tried to conceal the accident and delayed evacuation of people from nearby towns for days. Firefighters and other workers who were the first at the destroyed reactor had little or no protection from radiation.

More than 4,000 cleanup workers have died since and 70,000 have been disabled by radiation in Ukraine alone. About 3.4 million of Ukraine's 50 million people, including some 1.26 million children, are considered affected by Chernobyl.

A haphazardly built concrete and steel sarcophagus covers the ruined reactor, but it has developed leaks over the years. It emits high radiation levels and is also leaking water that may be contaminated.

The grayish Soviet-era structure is believed to contain up to 66 tons of melted nuclear fuel, in addition to some 37 tons of radioactive dust.

The covering now "automatically assumes a leading role. It's our largest project," said the structure's director, Valentyn Kupny.

Ukraine hopes to build a new, airtight covering over the sarcophagus as part of a $758 million international project running through 2007. But that will not solve the problem entirely, Kupny said.

"The work of handling the fuel remaining inside will take dozens of years," he said. "We'll have to work out an engineering decision on what to do with this fuel. At present, there is no such decision."